Process of manufacturing steel.



Patented March 8, 1904.

PATENT OFFICE.

OTTO MASSENEZ, OF WIESBADEN, GERMANY.

PROCESS OF MANUFACTURING STEEL.

SPECIFICATION forming part of Letters Patent No. 754,154, dated March 8, 1904."

Application filed Lpril 20, 1903. Serial No. 153,485. (No specimens.)

To all whom it may concern:

Be it known that I, OTTO MASSENEZ, doctor of laws, a subject of the King of Prussia, Emperor of Germany, whose post-oflice address is No. 10 Humboldstrasse, Wiesbaden, in the Kingdom of Prussia, German Empire, have invented a new and useful Process of Manufacturing Steel from Chromiferous Pig-Iron; and I do hereby declare that the following is a full, clear, and exact description of my invention, which will enable others skilled in the art to which it appertains to make and use the same.

This invention relates to the conversion of chromiferous pig-iron into steel; and it consists in the process hereinafter fully described, which enables steel to be manufactured from chromiferous pig-iron containing even more than one per cent. of chrome.

It is known that iron contammg a largepercentage of chrome is manufactured for the purpose of adding this alloy, which is called ferro-chrome,to the metal in the manufacture of steel in order to impart certain properties to the steel. Up to this day no other way of utilizing chromiferous iron in or for the manufacture of steel has been disclosed.

Sometimes iron is manufactured from iron ores which contain a small percentage of chrome, and the iron obtained from such ores can be worked without difliculty, owing to its very low percentage of chrome, whereas heretofore the use of raw iron rich in chrome as the starting metal with a view to making steel has not been realizable because of the inability of those skilled in the art to remove larger proportions of chrome from the pig-iron without disturbing the regular working or obtaining a serviceable quality of steel. It is well known that the attempts made in 1877 by E. Riley to manufacture malleable iron with iron obtained from Tasmania ores rich in chome have had no success, the only use of said iron having been'limited,and for a shortperiod, too, to that as an addition to the metal worked in the Martin furnace in order to impart to the product a definite percentage of chrome.

must be dissolved or taken up has imparted to it by the entrance of even a comparatively small proportion of chromic oxid such a degree of stiflness as precludes the finishing of the process. Ihave found that it is practicable to neutralize said stiffening action of the chromic oxid upon the slag to such an extent as to enable pig-iron containing a high percentage of chrome to be converted into steel in the reverberatory furnace. According to my present invention this neutralization of the stiffening action of the chromic oxid, or, in other words, the formation of a sufliciently. fluid slag, is obtained by adding certain fluxes to the chromiferous iron to be dechromized and converted. The flux or fluxes are added as soon as the formation of chromic oxid, and consequently the taking up of the same by the slag, sets in, which occurs immediately after the metal is melted down or, in case of liquid iron being charged into the furnace, immediately after the charging operation.

Fluxes suitable for my purpose are the chlorids and fluorids of the alkaline and alkalineearth metals, as also the carbonates of the alkaline metals and mixtures of two or more of the compounds mentioned, and I wish it to be understood that the term flux capable of counteracting the stiffening action of chromic oxid upon the.slag.as used in the annexed claims is intended to cover the use of any one of said compounds and of any mixture of them. The proportion of said fluxes to be added depends upon the weight of the charge to be treated, the percentage of chromium contained in the charge, and the nature of the flux employed. For instance, when fluor-spar is used as flux a charge of twenty tons containing two per cent. of chrome requires an addition of one ton and three-quarters of fluor-spar. Further, I have found that especially with charges containing more than two per cent. of chrome a considerable saving of both time and flux is obtained by adding the latter by portions.

In treating pig-iron containing a percentage of chrome less than two per cent. it is useful to remove a portion of the slag formed, whereas this removal of slag is indispensable when it is desired to manufacture a steel having a quite low percentage of chrome, as also when the proportion of chrome contained in the pig-iron exceeds two per cent. In any case it has been found necessary to cause so large a body of slag to be formed that the proportion of chromic oxid present in the slag does at no time surpass fourteen per cent, a higher proportion being apt to check proper working. For instance,a metal charge of twenty tons having three per cent. of chrome requires seven to eight tons of slag to be formed. Now this proportion of slag constitutes so large a mass as renders impossible to carry through the process without removing a considerable portion of the slag formed, for the reason that the latter would prevent proper action of the flame upon the metal bath. On the other hand, to give such large body of slag-sufficient fluidity for allowing the removal of the required proportion thereof to be performed in one operation such a quantity of fluxes would be needed as renders the process uneconomical. I have discovered that the addition of a comparatively small amount of fluxes (as compared with the body of slag) has the effect of imparting to the latter a certain degree of fluidity for a short period, after which it readily reassumes its stiffness. I profit from this discovery for facilitating the removal of the slag by operating the same by fractions-that is to say, by alternately adding a portion of flux and immediately withdrawing a portion of the thereby reliquified slag, this alternation of rel-iquifying the slag and removing part of the reliquified slag being repeated as often as is required to get rid of such an amount of slag as will allow the process to be accomplished.

In carrying out my invention with stationary furnaces I prefer to provide the latter with a special opening or openings for tapping or otherwise withdrawing the slag. When oscillatory hearth-furnaces are used, such opening or openings may be dispensed with. The fluxes should not be introduced into the furnace prior to or simultaneously with the charging in of the metal, as then the lining of the furnace will be attacked to a large extent, especially when simultaneously oxid of iron is added to the charge.

By means of my described process and in working charges containing one to five per cent. of chrome I have without difliculty succeeded in reducing this proportion of chrome down to three-tenths of a per cent. and a still smaller amount and in obtaining malleable iron with a desired percentage of carbon from such highly chromiferous iron.

Obviously reversal of the operation, so as to remove the metal instead of the slag and then finish the dechromized charge in another furnace or in the converter, involves no departure of my invention.

To reduce the cost for the large amount of slag required, the silicious slag obtained in the soaking-pit process may be used in my process with the addition of my said fluxes.

Owing to its large percentage of chromic oxid, the chromiferous slag obtained in my process can with advantage be utilized for manufacturing ferro-chrome with or without the addition of suitable chromic ores or for manufacturing chromates in well-known manner by mixing the finely-powdered slag with lime (chalk) or other suitable disintegrating agents, calcining in an oxidizing atmosphere, and converting the calcium chromate or other chromate obtained into chromates of the alakline metals. 7

What I claim as my invention is 1. The described process of manufacturing steel from chromiferous pig-iron in the reverberatory furnace which consists in melting the iron, forming in contact therewith a slag capable of dissolving chromic oxid, and adding a flux capable of counteracting the stiffening action of chromic oxid upon the slag, substantially as and for the purpose described.

2. The described process of manufacturing steel from chromiferous pig-iron in the reverberatory furnace which consists in melting the iron, forming in contact therewith a slag capable of dissolving chromic oxid, adding a flux capable of counteracting the stifiening action of chromic oxid upon the slag, and separating slag from the metal, substantially as and for the purpose described.

3. The described process of manufacturing steel from chromiferous pig-iron in the reverberatory furnace which consists in melting the iron, forming in contact therewith such a quantity of slag capable of dissolving chromic oxid that the resulting chromiferous slag does not contain more than fourteen per cent. of chromic oxid, adding fluxes capable of counteracting the stiffening action of the chromic oxid upon the slag, and separating slag from the metal, substantially as and for the purpose described.

4. The described process of manufacturing steel from chromiferous pig-iron in the reverberatory furnace which consists in melting the iron, forming in contact therewith such a quantity of slag capable of dissolving chromic oxid that the resulting chromiferous slag does not contain more than fourteen per cent. of

chromic oxid, repeatedly adding fluxes capable of counteracting the stiffening action of the chromicoxid upon the slag, removing a part of the slag after each addition of flux, and finally separating the remainder of slag from the metal, substantially as and for the purpose described.

5. The described process of manufacturing steel from chromiferous pig-iron, in the reverberatory furnace which consists in melting the iron, forming in contact therewith such a quantity of slag capable of dissolving chromic oxid that the resulting chromiferous slag does In testimony whereof Ihave hereunto set my nfit contain norgdthan fourteelrll pEr cent. of hand in presence of two subscribing Witnesses.- c rornic oXi a ing repeate y uor-spar, removing a part of the slag after each ad- OTTO MASSENEZ' 5 dition of fluor-spar, and finally separating the Witnesses:

remainder of slag from the metal, substan- HEINRICH JACOBS, tially as and for the purpose described. WILHELM QUITZDORFF. 

